Abstract:
The reef community at Cape Armitage was surveyed over two seasons (1987/88 and 1988/89). This community exists on a fan like shallow slope platform. In the same season, Pram Point was initially assessed and in this season (1991/92) the benthic community was investigated. In contrast to the shoal of Cape Armitage, the Pram Point reef is steeply sloping and provides an interesting contrast in ... habitat type. How the observed community structure at Pram Point originated and how it is maintained was examined. As in the earlier surveys at Cape Armitage, the marine benthos was surveyed with two 10m x 10m squares marked on the sea floor. Within each site, 6 random 1square meter quadrats were surveyed. All organisms within each quadrat were counted and measured. The reef community at Cape Armitage was resurveyed and compared with that of Pram Point. As echinoderms are known to be major community modifiers, a separate targeted survey was carried out on this group of mobile invertebrate predators.. The survey consisted of searching 10 randomly placed 1 square meter quadrats within each of the two 10m x 10m sites at each location. All asteroids and urchins were counted. In addition, all quadrats were searched in detail for reproductive propagules of sponges and indeed of other invertebrates. A targeted survey of Polymastia sphaerotylus which was found to be actively reproducing was initiated. This involved monitoring the presence or absence of propagules on ten randomly selected sponges at each site. Five specimens were collected for analysis. Sediment depth/quality was measured at both sites within each of the permanent quadrates and sediment traps set in place in 1987 were monitored. No sediment was detected suggesting that there has been no significant sedimentation of the reef in four years. Six replicate sediment samples were collected. This involved collection of sediments from randomly placed 30cm x 30cm quadrats to a depth of 4cm.